Esthetic wood product

ABSTRACT

METHOD FOR THE PREPARATION OF WOOD HAVING LONG LASTING ESTHETIC VALUE AND RESISTANCE TO WOOD DESTROYING ORGANISMS COMPRISING IMPARTING COLOR TO NON-PRESERVED WOOD WITH AN AQUEOUS PIGMENT COMPOSITION PRIOR TO TREATMENT WITH AN ORGANIC PRESERVING SYSTEM AND THE RESULTING WOOD PRODUCTS.

United States Patent 3,695,920 ESTHETIC WOOD PRODUCT Robert E. Hill, Clayton, Mo., assiguor to Koppers Company, Inc., Pittsburgh, Pa. No Drawing. Filed Apr. 20, 1970, Ser. No. 30,349

Int. Cl. B44d 1/16 US. Cl. 117-69 11 Claims ABSTRACT OF THE DISCLOSURE wood products.

This invention relates to a method of coloring and protecting wood and to the wood products so produced. More particularly, this invention relates to improving the esthetic value of wood resistant to wood destroying organisms.

There is a growing need for wood which is both acceptable to society from an esthetic standpoint and protected from wood destroying organisms. The common black wooden pole used in the distribution and transmission of energy is encountering serious difliculty in many areas of the United States. In some areas zoning laws require that all utilities be placed underground. In other areas utilities remain above ground but the color of the poles which can be used is governed by strict requirements.

Moreover, in the housing industry wood treated against wood destroying organisms is more acceptable if color is a matter of choice rather than determined entirely by the color of the preserving solution of the wood itself.

Color has been imparted to wood previously treated with an organic preserving system to improve the esthetic value in various ways. Oil-base paints and numerous pigmented latex coatings have been used but with only limited success. Numerous diverse coating materials do not adhere to the wood. The coatings blister, flake or chalk off of the wood in a short time, for example, about one year on wood preserved with an organic preservative system. This short period of color retention is not nearly coextensive with the useful life of the wood in most applications. The failure of most coatings on wood preserved with an organic preservative system can be traced to the treatment given the wood for protection against wood destroying organisms and/or the color coating system employed.

Although various compounds are used for the preservation of wood, pentachlorophenol has met with great commercial acceptance. In the usual wood preserving pressure processes pentachlorophenol dissolved in a suitable solvent is impregnated into the wood as by the well known pressure or thermal processes. The solvent is removed after impregnation by drying the wood. The pentachlorophenol penetrates into the wood and to a substantial extent remains impregnated in the wood after the solvent has been removed. One difficulty however is that there is a tendency for some of the pentachlorophenol to migrate out of the wood during both solvent evaporation and after the wood has dried. This phenomenon is referred to as blooming by the industry. The blooming of such phenolic compositions seriously affects the paintability of treated wood. In most instances the pentachlorophenol crystals must be removed prior to color coating. Another difficulty is that it is almost impossible to remove all of the solvent during drying. Some of the solvent for the pentachlorophenol not removed during drying will leach out of the wood over a long period of time. Thus oil-base paints and pigmented latex coatings applied to the wood do not adhere firmly and in a relatively short period of time adhesion is completely lost.

The wood cannot be coated for color with oil-base or latex paints and then treated with preservative since the preservative does not penetrate these coatings to an extent suflicient to be of value in preserving the pole. The oilbase coatings and latex-binder containing coatings make the poles non-breathable and the preservative will not penetrate. Moreover, many preservatives would destroy the oil-base or latex coating.

An object of this invention is wood having both long lasting esthetic value and protection against wood destroying organisms. Another object of this invention is a method for the preparation of wood having long lasting esthetic value and protection against wood destroying organisms.

The above and other objects of this invention are carried out by the method which comprises imparting color to non-preserved wood with an aqueous pigment composition prior to treating the wood with an organic preserving system. The method of this invention results in preserved wood having long lasting esthetic value. The wood after being colored by the aqueous pigment composition remains breathable and thus the preserving agent can readily penetrate into the wood. Blooming which may occur after preservation is not deleterious to the color coating since the color has already been imparted to the wooden member. Any such blooming does not cause the color to leave the pole as in the case of oil-base and latex-binder coatings since the color is bound by the wood and is not merely part of a binder system or coating thereon.

In carrying out the method of this invention any one of various well known methods of treating wood can be used depending on the desired treatment to the wood product and in particular the degree of penetration desired. In both the color imparting treatment and the preserving treatment such methods include brushing, spraying, dipping, soaking and the like, and thermal and pressure impregnation. Pressure treatments include empty cell and full cell procedures.

In the empty cell procedure the wood is placed in a pressure vessel, commonly a horizontal cylinder, and moderate air pressure is applied. An impregnant solution is forced into the cylinder and thus into the wood. Pressure up to about 200 p.s.i.g. is applied forcing the preservative solution deep into the wood. The pressure is released and the unabsorbed liquid is removed from the cylinder. A vacuum is applied, and the residual air in the lumins of the wood expands, thereby forcing the excess liquid from the wood. The wood cell walls are thus covered with microscopic droplets of the preservative solution.

The full cell pressure procedure involves the application of a high vacuum initially to the pressure vessel containing the wood. An impregnating solution is added to the cylinder and surrounds the wood while the vacuum is maintained. Positive pressure is then applied to force the impregnant into the wood. At the end of the impregnation period pressure is released, a final vacuum is applied and the unabsorbed liquid is removed from the cylinder. Various modifications of the empty cell and full cell procedures can be used, for example, the impregnating solution may initially be admitted to the treating cylinder under atmospheric pressure in either procedure or under a low vacuum.

The water dispersible pigments useful in the method of this invention include pigments well known to the art such as titanium dioxide white, yellow oxide, chrome yellow, Hausa yellow, azo yellow, molybdate orange, dinitroniline orange, toluidine red medium, red oxide light,

burnt sienna, ph'thalocyanine blue, phthalocyanine green, lamp black and the like.

The aqueous pigment compositions are prepared by adding water dispersible pigments and a dispersing agent to water and stirring. The pigment concentration in the aqueous pigment compositions may vary from about 0.001% to about 40% or more, depending on the intensity of color required on the treated wood. The aqueous pigment compositions useful in the method of this invention can also contain additional surfactants or wetting agents above the amount required for pigment dispersion in order to aid in dispersing the pigment into the outer fibers of the wood. The aqueous pigment compositions may be modified by the addition thereto of secondary materials, for example, extenders such as barium sulfate, zinc oxide, basic lead carbonate, calcium carbonate, silica and the various non-alkali metal silicates, adhesives and other materials having favorable action on the performance of the aqueous pigment composition and which do not interfere to any substantial extent with the breathability of the colored wood and thus the treatment with the preserving agent.

The preserving agent used in the preserving system for the method of this invention can be any known organic preserving agent for wood which does not adversely affect the color imparted by prior treatment With the aqueous pigment composition. Suitable preserving agents include creosote, halogenated hydroxy containing compounds, carbamates, nitrophenols, organo-tin compounds, organocopper compounds, organic arsenic compounds, halogenated and copper naphthalene derivatives, S-quinoline compounds such as 8-hydroxyquinoline, and esters of polychlorophenols such as the acetate, laurate and butyrate esters.

Halogenated hydroxy containing compounds suitable for the practice of this invention include halogenated monohydric phenols, halogenated polyhydric phenols and thiophenols and halogenated benzophenones and embrace halogenated parasiticidal phenols including alkyl and phenyl substituted phenols which have been chlorinated or brominated. Halogenated hydroxy compounds of particular value in the practice of this invention are those defined by a formula selected from the group consisting of (I) OH wherein R is selected from the group consisting of hydrogen, methyl, phenyl, chlorine and bromine, X is bromine or chlorine and n is an integer from 1 to 4 inclusive,

Y Y G X X wherein Y is OH or SH and is attached at the carbon atom in the 2 and 2' positions, X is chlorine or bromine and is attached at carbon atoms in the 4 and 4' or 5 and 5' positions of the phenyl rings.

Suitable monohydric halophenols are those having mixed chlorine and bromine as well as those having 'a single halogen species and include 2-bromo-4-chlorophenol, 2-bromo-4, 6-dichlorophenol, 2,3,6-tribromo-p-cresol, 2,4,6-trichloro-m-cresol, 2,4,6-tribromo-rn-cresol, 2,6-dibromo-4-chlorophenol, 2-chloro-4-phenylphenol,

2,3 ,4trichlorophenol,

2, 3 ,6-trichlorophenol, 2-bromo-4-phenylphenol, 4-bromo-2-phenylphenol, 4-chloro-2-phenylphenol, 4,6-dibromo-o-cresol, 2,5-dibromo-p-cresol,

3 ,6-dibromo-2-chloro-p-cresol 2,4,5-trichl0r0phenol, 4-bromophenol, 2-bromophenol, 2,4-dibromophenol, 4-chloro-m-cresol, 2-chloro-4,6-dibromophenol, pentachlorophenol, pentabromophenol,

2,3 ,5 ,6-tetrachlorophenol, 2,3 ,4,5-tetrachlorophenol, 2,3 ,4,6-tetrachlorophenol, 2,3,5 ,6-tetrachloro-p-cresol, 2,4,5,6-tetrabromo-m-cresol, 2,4,6-trichlorophenol,

3 ,4- dichloro phenol, 2,3-dichlorophenol, 2,5-dichlorophenol,

2, 6-dichlorophenol, 2,4-dichlorophenol, 4-chlorophenol, 3-chlorophenol and Z-chlorophenol.

Suitable polyhydric phenols and thiophenols and benzophenones, include 4,4'-dichloro-2,2'dithiophenol, 4,4-dibromo-2,2-dithiophenol, 4,4-dibromo-2,2-dihydroxybenzophenone,

5,5 '-dichloro-2,2-diphenol,

5,5 -dibromo-2,2'-diphenol, 4,4-'-dibromo-2,2'-dihydroxy diphenylrnethane and 2,2-dihydroxy-5 ,5 '-dichlorodiphenylmethane.

The organic preserving agents used in this invention are generally dissolved in organic solvents which are water immiscible and have a low pour point. Examples of organic solvents which can be used for the preserving agents include alcohols, esters, amides, ketones, ethers and acetals; organic phosphates and phthalates; aromatic hydrocarbon solvents such as benzene, xyleen, toluene, cumene, mesitylenes and alkylnaphthalenes, and various petroleum products such as liquid petroleum gas, kerosene, mineral spirits, Stoddard solvent and the like. Mixtures of these solvents can also be employed.

The two types of solvents are those that remain in the wood holding the preservative in solution and those that are volatile and deposit the preservative in the wood after solvent evaporation. The solvents that remain in the wood have a preferred initial boiling point above about 350 F. and a preferred 50% point above 500 F. Solvents that do not remain in the wood have a preferred boiling end point below about 400 F.

In either the aqueous pigment composition or the organic preserving composition used in accordance with this invention, a sequestering agent may be added to prevent precipitation of calcium and magnesium soaps. A sequestering agent particularly useful in the practice of this invention is an aqueous solution of the tetrasodium salt of ethylenediaminetetraaoetic acid (commercially available as Versene Powder, Versene 67, Versene 100). Other sequestering agents Which can be used include the disodium salt and the trisodium salt of ethylenediaminetetraacetic acid and mixtures thereof.

Wood which can be colored and preserved in accordance with the present invention are the green or seasoned hardwood and softwood. Illustrative varieties of hardwood being birch, maple, beech, ash, mahogany, walnut, hickory, gum and oak. Illustrative varieties of softwood being southern pine, ponderosa pine, Douglas fir, hemlock, western larch, jack pine, lodgepole pine, red pine, northern white pine, sugar pine, western white pine, red cedar and white cedar.

The method of this invention is particularly useful for treating such wood products used as energy distribution and transmission poles, cross arms, fence posts, and for floors and platforms and the like.

The following examples will illustrate the invention. Parts and percent are by weight unless otherwise indicated.

EXAMPLE 1 Southern yellow pine poles are colored gray by brushing with an aqueous pigment composition comprising 75% water, 24.94% Ti and 0.06% lamp black, dried for 24 hours at about 25 C. and pressure treated with a preservative composition comprising 86 parts Stoddard solvent, 7 parts pentachlorophenol and 7 parts polyalkyleneglycol ether by the empty cell procedure to a retention of 6 pounds preservative per cubic foot of wood. The poles are placed in the vertical position in an outside test yard. After about ten months the poles do not exhibit any loss of color from the environment or damage from wood destroying organisms.

EXAMPLE 2 V-shaped sections each containing a large colored surface area are cut from the outside surface of the test poles of Example 1 after the test poles have been in the yard about three months. The V-shaped sections are placed in a four carbon rod Atlas Weatherometer and subjected to alternating water spray at a temperature of about 120 F. for accelerated exposure. After about five weeks of accelerated exposure (equivalent to about 17 months of normal exposure) the colored sections do not exhibit any sign of color loss.

The embodiments of this invention in which an exclusive property or privilege is claimed are defined as follows:

1. Method of producing wood having long lasting esthetic value which is also resistant to Wood destroying organisms comprising imparting color to non-preserved wood with an aqueous pigment composition prior to treatment with an organic preservative system comprising an "organic solution of an organic soluble preservative, wherein said aqueous pigment composition is substantially free of materials which adversely affect the treatment with organic soluble preservative and wherein the organic soluble preservative does not adversely affect the color imparted by prior treatment with the aqueous pigment composition.

2. Method of claim 1 wherein. the preservative is a polychlorophenol.

3. Method of claim 2 wherein the polychlorophenol is pentachlorophenol.

4. Method of claim 1 wherein the preservative is an ester of pentachlorophenol.

5. Method of claim *1 wherein the wood is in the form of a pole.

6. Method of claim 1 wherein the organic soluble preservative is dissolved in a light colored solvent.

7. Method of claim 1 wherein the pigment imparts a gray color.

8. Method of claim 1 wherein. the pigment imparts a gray color and the preservative is pentachlorophenol or tributyl tin oxide dissolved in a light colored solvent.

9. Method of claim 1 wherein the preservative is tributyl tin oxide.

10. Method of claim 1 wherein the preservative is copper naphthalate.

11. Method of claim 1 wherein the preservative is copper 8-quinolinolate.

References Cited UNITED STATES PATENTS 1,043,582 11/1912 Fallen 8-6.5 3,266,981 '8/1966 Stern et a1 21-7 X 2,382,374 8/1945 Wood 117-116 3,539,289 11/1970 Suzuki et all 117-147 X 3,467,546 9/1969 Page et al. 117-116 3,333,977 8/1967 Clark et al 117-57 X 3,180,746 4/1965 Patton et al 117-147 X 3,070,494 12/1962 Goldstein et a1. 117-147 X 2,565,602 8/1951 Fisher et al. 117-57 2,308,491 1/1943 Conger 117-117 RALPH S. KENDALL, Primary Examiner C. WESTON, Assistant Examiner US. Cl. X.R. 

